A review that covered nearly 20 million people has confirmed that people with diabetes face a higher risk of cancer, and that risk is higher among women than men.

Findings published in Diabetologia, the journal of the European Association for the Study of Diabetes, showed that women with type 1 of type 2 diabetes were particularly at risk for cancers of the stomach, mouth, and kidney.

The authors reviewed articles appearing in PubMed through December 2016, and ended up including data from 106 articles in the study. This allowed the review to evaluate gender-specific effects of diabetes on overall cancer risk as well as 50 site-specific cancers.

Results covered data from 47 countries. Authors called it “the most comprehensive analysis to date on the sex-specific effects of diabetes on cancer risk.”

Overall, the review showed diabetes is a risk factor for most cancers, and that women with diabetes were 6% more likely than men with the disease to develop some form of cancer. Among people with diabetes, researchers also found:

Women were 27% more likely to develop cancer than those without diabetes. Men faced a 19% higher risk of cancer.

Of note, women faced an 11% higher risk of kidney cancer, a 13% higher risk of oral cancer, a 14% higher risk of stomach cancer, and a 15% higher risk of leukemia than men.

Liver cancer was an exception: the risk for women with diabetes was 12% lower than that of men.

Sanne Peters, PhD, of The George Institute for Global Health at the University of Oxford and a study coauthor, said that women may be more likely to develop cancer than men with diabetes because they are in prediabetes longer than men; typically, women develop impaired glucose tolerance that goes unaddressed for up to 2 years longer than men.

“Historically, we know that women are often untreated when they first present with symptoms of diabetes, are less likely to receive intensive care and are not taking the same levels of medications as men,” Peters said in a statement. “All of these could go some way into explaining why women are at greater risk of developing cancer. But without research we can be certain.”

Peters and lead author Toshiaki Ohkuma, a research fellow at the Global Institute, said the results show why gender-specific research is important. While the link between diabetes and cancer has been known for some time, Ohkuma said, “We have also demonstrated for the first time that women are more likely to develop any form of cancer, and have a significantly higher chance of developing kidney, oral, and stomach cancers, and leukemia.”

Elevated blood glucose seen in diabetes is believed to damage DNA, causing cancer. However, the authors wrote, “Further studies are needed to clarify the mechanisms underlying the sex differences in the diabetes–cancer association.”

More than 30 million people in the United States have diabetes, with 95% of the cases being type 2 diabetes. Worldwide, more than 415 million people have the disease.

Reference
Ohkuma T, Peters SAE, Woodward M. Sex differences in the association between diabetes and cancer: a systematic review and meta-analysis of 121 cohorts including 20 million individuals and one million events. Diabetologia, 2018. doi: 10.1007/s00125-018-4664-5.